I'm just posting this because I had a similar (but different) problem. (I had no video output to my video players, e.g. Realtime, Media Player, VLC, but I had audio. I could also watch most stuff on Youtube.) Various sites said e.g. to download codecs, update video driver, adjust hardware settings for acceleration. None of that worked for me. In my case, I have some software the computer that controls various video settings. (My computer is a Lenovo and has a program called Catalyst ATI.) It turned out that this program was the problem. There was a setting in the program for the quality of the output, e.g. home, theater, office and "custom." Mine was set to custom, and when I changed it to "home," voila, everything was working again. So, here are 4 ideas in total for this problem.